Fig. 1 (from Lebreton et al., 2009). Regions in which gray matter density (GMD) is associated with reward dependence. Mean gray matter density was extracted from each of the clusters that we identified using linear regression, transformed into Z-scores, and plotted versus RD. The lines represent the best fit for the associations when adjusted for total gray matter volume.

To be fair to the authors, they never used the expression "people person" in their paper. That was the BBC1, among other press outlets:

Scientists say they have located the brain areas that may determine how sociable a person is.

Warm, sentimental people tend to have more brain tissue in the outer strip of the brain just above the eyes and in a structure deep in the brain's centre.

These are the same zones that allow us to enjoy chocolate and sex, the Cambridge University experts report in the European Journal of Neuroscience.

. . .

The men who scored higher on questionnaire-based ratings of emotional warmth and sociability had more grey matter in two brain areas - the orbitofrontal cortex and ventral striatum.

As we can see in Figure 1, however, the gray matter volume in other brain areas (as measured using voxel-based morphometry) was also correlated with social reward dependence, defined as

a stable pattern of attitudes and behaviour hypothesized to represent a favourable disposition towards social relationships and attachment as a personality dimension.

Social reward dependence (RD) was measured using

the RD scale of Cloninger’s temperament and character inventory (TCI), a questionnaire that maps independent temperament traits onto putatively independent neurobiological systems (Cloninger, 1987, 1994). The RD subscale measures the tendency of subjects to be sensitive to a socially defined reward: a high score indicates a high disposition to social relationships and attachment; and a low score indicates a tendency to insensitivity and aloofness.

The participants were drawn from a large cohort of Finnish people born in 1966:

Data on biological, socioeconomic and health conditions, living habits, and family characteristics of cohort members were collected prospectively from pregnancy. The present study is based on 10,934 individuals living in Finland at the age of 16 years who did not forbid the use of their data...

Of that gigantic cohort, the authors restricted subject selection to 4,349 people (1,974 males) who had completed the TCI questionnaire. Of the 1,531 living in the city of Oulu, 187 subjects were randomly selected and invited to participate, and 104 (62 men) agreed to have an MRI. The authors excluded female participants from the present study because they're more emotional and different from men [basically]. And it turned out that TCI data were not available from 21 of the 62 men after all, so the final sample was comprised of 41 male volunteers.

Voxel-based morphometry was used to create probabilistic maps of gray matter for each individual. Associations between RD and brain structure were corrected for total gray matter volume and tested by fitting a multiple linear regression model at each voxel, followed by permutation testing. Out of the blue (with no previous or subsequent mention), the authors also decided to adjust for novelty seeking and harm avoidance. Lebreton et al. found the predicted correlation of RD and GMD in the orbitofrontal cortex (OFC) and the ventral striatum. They didn't have much to say about why the inferior temporal gyrus2 and cerebellum showed positive/negative correlations with RD, though. In the BBC article,

Professor Simon Baron Cohen, of the Autism Research Centre in Cambridge, said: "This is an important study in showing that the degree to which we find socializing rewarding is correlated with differences in brain structure.

"It reminds us that for some people, socializing is an intrinsic reward, just like chocolate or cannabis. And that what you find rewarding depends on differences in the brain.

Will we now see neurotraining programs designed to increase the size of your OFC and ventral striatum?

Thursday, May 14, 2009

Seasonal affective disorder (SAD) is a cyclical depressive disorder that typically recurs every year during the shorter days and longer nights of late fall-early winter. Much of the research on SAD has focused on changes in the photoperiod and the accompanying effects on circadian rhythms during winter. So it might come as a surprise that in Greenland, the suicide rate peaks during the summer months of continuous sun (especially at the highest latitudes). However, the rate of homicides and the sales of beer do not show the same seasonal variation (Björkstén et al., 2009).

Why might this be? Most suicides in Greenland are of the impulsive variety and are committed using violent methods. The authors' previous work observed the summer suicide spike (Björkstén et al., 2005), and now they wanted to determine whether homicides show the same seasonal pattern. They reviewed the evidence on serotonin, impulsivity, and violence, and hypothesized that altered serotonin turnover might be a common factor in both violent suicides and violent homicides (reasoning that increased serotonin turnover in spring and summer might enhance impulsiveness and aggression).

How was this assessed? Northern Greenland (obviously) shows the greatest seasonal extremes in the amount of light and darkness. The country maintains good statistics, and the Inuit population is considered to be relatively homogeneous. Thus, Björkstén, Kripke, and Bjerregaard (2009) examined computerized records listing the causes of all deaths in Greenland during the time period of 1968-2002. To determine whether alcohol consumption played a role in the rates of suicides and murders, the pattern of beer purchases at a major chain store from July 2005 to June 2006 were used as a proxy ("Detailed sales data are secret for business reasons").

The authors note some extremely tragic statistics:

The suicide rate in Greenland increased during the 1970’s from a historically very low level to one of the highest levels in the world, 107 per 100,000 person-years in 1990-1994. The increase has been most pronounced among teenagers and young adults. A rapidly increasing suicide rate has been reported from other areas going through radical changes like in Eastern Europe after the fall of communism and among aboriginal people confronted with modern lifestyle.

We have previously demonstrated that the vast majority of suicides in West Greenland are violent and peak in the summer when the Northern half of Greenland has constant day-light and the Southern half has extremely long days. Depression has, however, been reported uncommon and the majority of suicides seem impulsive rather than depressive.

The overall homicide rate in Greenland has been reported much higher than that of the other Nordic countries. Homicides are almost exclusively impulsive and committed under the influence of alcohol...

Continuing in a depressing vein, there were 1351 suicides (80.5 % were men) and 308 homicides during the 35 year period under study.

Persons in upper teens and young adults were heavily over-represented among the suicide cases. Median age was 25 years...

In 391 out of the 1351 cases (29%), the death certificate included a psychiatric diagnosis. In 214 cases (15.8%), there was a diagnosis of alcoholism or alcohol intoxication; two cases also had a diagnosis of psychosis. In only 52 cases (3.8%), there was a diagnosis of affective disorder, either unspecified or in the depressive state. In 104 cases, there was a diagnosis of psychosis. In addition to the 104 cases (7.7%), there were two with alcoholism and psychosis.

However, affective disorders could have been underdiagnosed in the population... we don't really know for sure. What we do know is that violent methods of suicide were used in 95% of all cases (n=1286), with men using violent methods 97% of the time and women 86% of the time (the latter percentage in stark contrast to the general population outside of Greenland). Figure 3a below shows the seasonal variation in all suicide cases. The annual peak occurred on June 11th and the trough in November-January, and the effect of seasonality was significant (p<0.001). For homicides (Fig. 3b), the calculated annual peak occurred on May 2nd, but the seasonal variation in homicides did not reach significance (p<0.10).

Figure 3 (Björkstén et al., 2009). Monthly distributions of suicides and homicides. The monthly distribution of all suicides (n=1351) is shown in Fig 3a and all homicides events (n=286) in Fig 3b. Please note that the scales on the Y-axes are different.

Finally, the seasonality effect for suicide was greater for those living above the Arctic Circle.

Conclusions

Suicides were almost exclusively violent with significant summer peaks when there is either midnight sun or very long days. The suicides were more concentrated around the summer months at higher latitudes. At about 77ºN, 82% of the suicides occur during the period of constant day.

In 29% of the suicide cases, there was a psychiatric diagnosis in the death certificate, however rarely depression (3.8%).

Homicide deaths showed a non-significant increase in spring, and the rate was high compared to other Nordic countries.

There was a bi-phasic seasonal variation for suicides related to alcohol, but no seasonal variation in consumption of beer.

Light is only one of many factors in the complex tragedy of suicide, but this study shows that there is a possible relationship between light and suicide.

Tuesday, May 12, 2009

The goal of the Biologically-Inspired Cognitive Architectures Program via this BAA is to develop, implement and evaluate psychologically-based and neurobiologically-based theories, design principles, and architectures of human cognition. In a subsequent phase, the program has the ultimate goal of implementing computational models of human cognition that could eventually be used to simulate human behavior and approach human cognitive performance in a wide range of situations.

Two anonymouscommenters on my previous post about the PI Program at DARPA (Defense Advanced Research Projects Agency) noted the existence of an earlier program that never got off the ground. Neither commenter had particularly fond memories, likening it to a Survivor-like battle between huge alpha male egos out for a money grab.

The second phase (Implementation) of BICA was set to begin in the spring of 2007, and would have involved the actual construction of new intelligent agents that live and behave in a virtual environment. However, this phase was canceled by DARPA, reportedly because it was seen as being too ambitious.

How ambitious? For example, APPENDIX ONE: Functional Primitives of the Human Brain (An Initial List) (keep scrolling) is a modest list of 400 or so cognitive, linguistic, social, emotional, sensory, and motor functions that range from imprinting to combinatorial creativity to gustatory learning to frustration. How many of these could be incorporated into a model of human cognition??

Under Task 1, developers will produce psychologically-based theories of cognition covering as broad a range of cognitive activities as possible.

In the end, it became clear that the whole idea was unfeasible. DARPA was not deterred by that experience, however, because the Physical Intelligence Project seems even more ambitious, with the following goal:

If successful, the program would launch a revolution of understanding across many fields of human endeavor, demonstrate the first intelligence engineered from first principles, create new classes of electronic, computational, and chemical systems, and create tools to engineer intelligent systems that match the problem/environment in which they will exist.

Monday, May 11, 2009

Colossus - The Forbin Project takes place in the 50s during the height of the cold war. Dr. Charles Forbin, a genius scientist who has lost trust in humanity’s ability to logically address emotional issues, has developed a very special computer to perform the Strategic Air Command and Control functions for the military. This computer, code named Colossus, is developed based on incredible advances in Artificial Intelligence, and has a logical process for determining when to launch the ICBMs. With much fanfare, the President of the US “turns on” Colossus to take over responsibility for the US nuclear armament. [from Cyberpunk Review]

The workshop goals are to: (a) introduce the research community (industry, academia, and Government) to the PI program vision and goals; (b) explain the mechanics of a DARPA program and the milestones and metrics of this particular effort; and (c) promote teaming arrangements among organizations having relevant expertise, facilities, and capabilities to execute an interdisciplinary research program responsive to the PI program goals. The workshops will include overview presentations by Government personnel and poster sessions to facilitate interaction and team building among the session participants.

The workshops will be held June 9, 2009, 7:00am-5:00pm in Reston, VA and June 11, 2009, 7:00am-5:00pm in San Jose, CA. See this link for more information.

Others have already written about the new voodoo-esque paper by Kriegeskorte et al. (2009). Having blogged extensively about the original controversy, I don't have anything to add... other than the links above... and some fun and wholesome pictures.

A neuroscientific experiment typically generates a large amount of data, of which only a small fraction is analyzed in detail and presented in a publication. However, selection among noisy measurements can render circular an otherwise appropriate analysis and invalidate results. Here we argue that systems neuroscience needs to adjust some widespread practices to avoid the circularity that can arise from selection. In particular, 'double dipping', the use of the same dataset for selection and selective analysis, will give distorted descriptive statistics and invalid statistical inference whenever the results statistics are not inherently independent of the selection criteria under the null hypothesis. To demonstrate the problem, we apply widely used analyses to noise data known to not contain the experimental effects in question. Spurious effects can appear in the context of both univariate activation analysis and multivariate pattern-information analysis. We suggest a policy for avoiding circularity.

Wednesday, May 06, 2009

If you are better at exerting self-control by choosing less pleasurable but more healthy options, do you live in a constant state of (suppressed) desire? If you feel like you're always sacrificing and denying yourself what your brain's "valuation system" indicates is worth more, does the craving eventually go away? Or are you more likely to binge in a moment of weakness? Isn't this why most diets fail? Wouldn't it be better to have that candy bar every once in a while? (or else, learn to love cauliflower more than Cadbury)?

Study of dieters shows how two brain areas interact in people with the willpower to say no to unhealthy foods

PASADENA, Calif.--When you're on a diet, deciding to skip your favorite calorie-laden foods and eat something healthier takes a whole lot of self-control--an ability that seems to come easier to some of us than others. Now, scientists from the California Institute of Technology (Caltech) have uncovered differences in the brains of people who are able to exercise self-control versus those who find it almost impossible.

The key? While everyone uses the same single area of the brain to make these sorts of value-laden decisions, a second brain region modulates the activity of the first region in people with good self-control, allowing them to weigh more abstract factors--healthiness, for example--in addition to basic desires such as taste to make a better overall choice.

"We recruited two types of subjects: 1) individuals who self-reported being on a diet to lose or maintain weight and 2) individuals who self-reported no current monitoring of their diet. All subjects reported that they enjoyed eating sweets, chocolate, and other “junk food” even though they might be restricting them from their current diet.

. . .

Subjects were classified as self-controllers (SC) or non-self-controllers (NSC) based on their behavior during the experiment, and not on their self-reports about diet status during the recruiting process."

So really, the study isn't about dieting at all,1 because one could be a "self-controller" in the experiment and yet report no dietary restrictions in real life. And actually, the study may not even say much about food choices in the real world, because a participant could say she'd choose the broccoli over the brownie to gain the experimenter's approval, but then go home and eat ice cream for dinner.

Back to the subject selection:

"Fifty-two subjects participated in the experiment. However 15 subjects did not meet our a priori inclusion criteria based on their behavioral data [they fell into a gray zone]. 37 subjects were included in the analysis. Subjects were divided into two groups based on their behavioral data: successful self-controllers (SC) and non-self-controllers (NSC). The SC group included 19 subjects (14 female ... mean BMI = 24.8 ± 5.2) and the NSC group included 18 subjects (6 female ... mean BMI = 23.2 ± 5.1)."

There's a lot more pressure on women to diet and to give the appearance of restraint, and 70% of them were in the SC group. So who knows, it might be true that the female subjects felt more compelled to choose the healthy choice than they would have in real life.

The subjects viewed pictures of 50 different food items and rated them on a 5 point scale for health and taste in two separate blocks. After this, one food item rated as neutral on both dimensions (e.g., crackers, jello) was selected as the reference item, and subjects had to choose between it and another item on each trial.

"Subjects cared about their choices because they were required to eat the food that they chose in a randomly selected trial at the end of the experiment.2 Note that because subjects did not know which trial would count, their optimal strategy was to treat each decision as if it were the only one that counted. Although this is a binary decision task, subjects were asked to express the strength of their preferences using a five-point scale: Strong No (=choose reference) [to] Strong Yes (=choose shown item)."

The participants were sorted into SC and NSC groups according to their behavioral performance during the decision phase. The SC subjects chose food items on the basis of both health and taste, but the NSC group chose on the basis of taste alone. What were the investigators looking for in the fMRI data? They assumed at the outset that the brain's "value assigner" is located in the ventromedial prefrontal cortex3 (vmPFC), and the "self-controller" (in the dorsolateral prefrontal cortex, DLPFC) modulates value signals in vmPFC.

Fig. 2E. Robust linear regression showing a strong relationship between a measure of the effect that health ratings have on vmPFC activity and a measure of the effect that the health ratings have on decisions.

Below is another figure showing that Beta values in vmPFC increased with goal values, regardless of self-control. The legend was taken from Hare et al., Supporting Online Material (PDF).

Fig. 2B (Left).Estimated betas in the vmPFC for each of the regressors. This plot was constructed as follows. First, for each individual and type of trial we measured the associated beta value at the peak voxel for the goal value contrast (GLM 1) inside the vmPFC ROI shown in Fig. 2A (Right). The individual subject peaks were selected from within this ROI to allow for variability between subjects. Second, the mean and standard error of these betas were computed for each type of trial.

Now what about self-control in the DLPFC? A region in the left middle and inferior frontal gyri (IFG/BA 9) was more active during "self-control" trials in both groups, with the SC group showing this to a greater extent than the NSC group. And finally there was the requisite functional connectivity analysis (PDF) to explain the inverse relationship between greater activation in IFG/BA 9 and reduced activation in vmPFC. But since these two regions did not exhibit task-related functional connectivity, another area (IFG/BA 46, of course) had to be mediating the self-controlling effect of IFG/BA 9 on vmPFC. Got that? Hmm.

One of the things that struck me about this paper4 is the remarkable lack of scholarship, particularly when concluding in such a grandiose fashion:

"Lastly, an improved understanding of the neurobiology of self-control in decision-making will have applications to clinical practice in domains such as obesity and addiction, to economic and public policy analysis in problems such as suboptimal savings and health behaviors, and to legal thinking about which criteria should be used in determining if an individual is in full command of his decision-making faculties and thus accountable to the law."

Let's take the applications for obesity as our most relevant example here. Were there any citations of the literature on neurodegenerative disorders and appetite? Case studies of brain lesions and appetite? Studies of obese vs. lean individuals? Eating disordered vs. normal weight people? No, no, no, and no. Since they didn't cite any papers in these important [and more ecologically valid, if you really want to learn about self-control over food choices] areas of inquiry, here's what I learned from a PubMed search. A voxel-based morphometry study in patients with frontotemporal dementia demonstrated that binge eating was associated with greater degeneration in the right ventral insula, striatum, and orbitofrontal cortex (Wooley et al., 2007). Conversely, tumors in the right lateral frontal cortex have been associated with anorexia in several case reports (Houy et al., 2007; Trummer et al., 2002). In healthy subjects, transcranial direct current stimulation over DLPFC (specifically to increase neuronal firing over the right and to decrease it over the left DLPFC) was shown to reduce food cravings (Fregni et al., 2008). Neuroimaging studies have observed less activation in the left DLPFC of obese participants after a meal than was observed in lean participants (Le et al., 2006, 2007). There's even a right PFC hypothesis of obesity (Alonso-Alonso & Pascual-Leone, 2007).

You'd think all of this might have been relevant to an article on the neurobiology of self-control over food choices, but apparently not. Time for some chocolate cake. I just can't help myself...

Footnotes

1The writer of the press release can be excused for getting this wrong because in the main article, Hare et al. lead the reader to believe that the subjects are all dieters:

To test these hypotheses, we recruited self-reported dieters and used functional magnetic resonance imaging (fMRI) to study the neural activity in vmPFC and DLPFC while the participants made real decisions about which foods to eat.

2 At the end of the experiment, were the participants asked how much they really cared about their choices, or is that just a proclamation?

3 The words dopamine, nucleus accumbens, and basal ganglia did not appear in the article (ignoring previous studies on the topic). The phrase "vmPFC-striatal network" appears once but is dissed right away.

Introduction: The concept of self-control in decision-making has occupied philosophers and scientists throughout recorded history because the ability to exercise it is central to human success and well-being. Behavioral studies have examined the problem of self-control and provided valuable insights that suggest it is exhaustible in the short term (1–3), can be enhanced by cognitive strategies (4–7), and is correlated with measures of intelligence (8–10). However, little is known about the neurobiological underpinnings of self-control and how these neural mechanisms might differ between successful and unsuccessful self-controllers.

I told myself it would be different when I had children. We'd share our experiences and feelings together. We'd be so close. But I'm just like my father, a drunken slob. And the only feelings I share are no, no feelings at all. The only feelings I share are no feelings at all.

Saturday, May 02, 2009

The concept of _____________ has occupied philosophers and scientists throughout recorded history because the ability to _________ is central to human ________ and ________. Behavioral studies have examined the problem of ________ and provided valuable insights that suggest it is __________ (1–3), can be enhanced by ___________ (4–7), and is correlated with _____________ (8–10). However, little is known about the neurobiological underpinnings of ___________ and how these neural mechanisms might differ between ___________ and __________.

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About Me

Born in West Virginia in 1980, The Neurocritic embarked upon a roadtrip across America at the age of thirteen with his mother. She abandoned him when they reached San Francisco and The Neurocritic descended into a spiral of drug abuse and prostitution. At fifteen, The Neurocritic's psychiatrist encouraged him to start writing as a form of therapy.